Chapter 5
Signal Connections
NI PCI-7342 Hardware User Manual
5-8
ni.com
Figure 5-4.
Limit and Home Input Circuit
Caution
Excessive input voltages can cause erroneous operation and/or component
failure. Verify that your input voltage is within the specification range.
Encoder Signals
The PCI-7342 controller offers two channels of single-ended quadrature
encoder inputs. All National Instruments power drives and UMI
accessories provide built-in circuitry that converts differential encoder
signals to single-ended encoder signals. Each channel consists of a
Phase A, Phase B, and Index input, as described in the following sections.
Encoder <1..2> Phase A/Phase B
The encoder inputs provide position and velocity feedback for absolute
and relative positioning of axes in any motion system configuration.
If you do not need an encoder resource for axis control, you can use it for
other functions, including position or velocity monitoring, digital
potentiometer encoder inputs, or as a master encoder input for master/slave
(electronic gearing) applications.
A field-programmable gate array (FPGA) implements the encoder channels
(Encoder <1..2>). The encoders are high-performance with extended input
frequency response and advanced features, such as high-speed position
capture inputs and breakpoint outputs. Their maximum count frequency is
20 MHz.
An encoder input channel converts quadrature signals on Phase A and
Phase B into 32-bit up/down counter values. Quadrature signals are
generated by optical, magnetic, laser, or electronic devices that provide
two signals, Phase A and Phase B, that are 90° out of phase. The leading
phase, A or B, determines the direction of motion. The four transition states
of the relative signal phases provide distinct pulse edges that cause count
up or count down pulses in the direction determined by the leading phase.
From the External
Connector Limit
and Home Switch Pins
To the Limit and
Home Switch
Circuits
3.3 k
Ω
DGND
Vcc
74HC244
1 k
Ω
1/8 W
